Insulator



June 11, 1929. THOMSON LTI'ZCZZBI I INSULATOR Filed March 2, 1927Inventor: Elihu Thomso His i kc'borneg.

Patented June 11, 1929 UNITED STATES 1,717,281. PATENT OFFICE.

ELIHU THOMSON, OF SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR T GENERAL ELEG-TBIC COMI'ANY, A CORPORATION OF NEW YORK.

IN SULATOB.

Application filed March 2, 1927. Serial No. 172,117.

My invention relates to insulators and has for its object a simple andrugged insulator in which provision is made for preventing failure ofthe insulator due to electrical dis- 5 charges over its surface.

My invention has particular application to insulators which have apotential gradient,

over their outer surfaces whereby they are subject to electricaldischarges over their outer surfaces, such as strain insulators forelectric lines, spark plugs, etc. Insulators of this type 7 very oftenreceive gradual accumulations of dust and other substances which have amuch higher electrical conductivity than the insulator itself. Thesedeposits eventually result in an electrical discharge over the surfaceof the insulator. Glass, porcelain and various other insulatingmaterials ordinarily used are often splintered or carbonized somewhat 2when subjected to such electrical discharges, .whereby the efficiency ofthe insulator is greatly impaired.

In carrying out my invention I insert strips of quartz material in theinsulator, which strips roject from the insulator and extend in adirection transverse to the potential gradient over the surface of theinsulator. These strips of quartz are not damaged by flash-overs andconsequently the accumulations of dust or other material are burned offwithout appreciable detrimental effect on the insulator.

For a more complete understanding of my invention reference should behad to the accompanying drawing, the four figures of which are sideviews partly in section showing various forms of electric insulatorsconstructed in accordance with m invention.

Referring to the drawing I have shown my invention as applied to straininsulators, such as used on electric power lines. This insulatorcomprises two metallic members 10 and 11 which are somewhat similar tothe links of a chain and are interlinked with each other in a similarmanner. The links, however, are embedded in spaced relation in asuitable insulating material 12 which may be molded into the desiredform, shown as substantially cylindrical.- The links are therebyelectrically insulated from each other by the insulating material 12which may be any suitable material, such as glass, porcelain, bakelite,etc. The rojecting ends of the links are provided witli eyelets 13 and14 to facilitate the attachment of wires thereto, one or both of whichmay be connected to a high tension electrical supply source.

The potential difference, which may be very great, between the two linkmembers 10 and 11 results in a potential gradient between the twomembers over the surface of the insulating material in which they areembedded. It will be readily understood that deposits of dust and otherforeign material which may accumulate on the insulator may in time forma path of suflicient conductivity over the surface of the insulator toproduce an electrical discharge over the surface. This discharge burnsaway the accumulated material, but with the usual insulating materials,such as glass, porcelain, etc., the material of the insu ator itself maybe decomposed or carbonized somewhat or injured so as to impair theefficiency of the insulator.

In accordance with my invention I provide barriers on the surface of theinsulator extending transversely to the potential gradient made of anelectrically insulating material which is not injured by theelectricaldischarges. I have found that quartz is a very suitable material forthis purpose. In the form shown in Fig. 1a plurality of rings 15 made ofquartz are embedded in the insulating material 12 so as to projecttherefrom an appreciable distance. In the form shown in Fig. 2 ahelically formed quartz strip 16 is embedded in the insulating material.Fig. 3 shows a plurality of relatively short quartz strips 17 which areembedded in the insulating material in staggered relation. In Fig. 4 thequartz strips 18 are somewhat greater than semicircles and are placed instaggered relation on the insulator. As shown in the drawing the rings15 and strips 16, 17 and 18 are wider at the inner ed es and thus aresecurely held imbedded in t e insulating material 12. With thisarrangement the required insulation properties are maintained by thequartz barriers, which are not injured by electrical discharge, eventhough the insulating material 12 may become a partial conductor on itssurface.

While I have described my invention as embodied in concrete form and asoperating in. a specific manner in accordance with the provision of thepatent statutes, it should be understood that I do not limit myinvention thereto since various modifications thereof will suggestthemselves to those skilled in the art Without departing from the spiritof my invention the scope of which is set forth in the annexed claims.

Nhat I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an insulator having a potential gradient across its surface, abody of molded insulating material, a plurality of projecting strips ofquartz imbedded in said material forming barriers for electricaldischarge over the surface thereof.

2. An insulator comprising a body of insulating material, and aprojecting member made of quartz imbedded in said body and extendingtransversely to the potential gradient on the surface of the insulator.

3. An insulator comprising a body of molded insulating material, andstrips of quartz embedded in said material and projecting from saidbody, said strips extending in a direction transverse to the potentialgradient across the surface of said insulator.

In witness whereof, I have hereto set my hand this twenty eighth day ofFebruary,

ELIHU THOMSON.

